It is known how to measure the flow rate of the smokes, by using a tracer entering the system mixed with the blowing oxygen, and is subsequently defined in the smokes by means of a mass spectrometer.
By denoting with q.sub.A the flow rate of the marking gas and with C.sub.A the concentration thereof outcoming from the converter opening, the flow rate of the smoke Q.sub.F is given by: EQU Q.sub.F = q.sub.A / C.sub.A ( 1)
Said tracing gas is an inert gas which does not take part in the reactions occurring inside the converter during the refining, the gas used as a tracer being preferably formed by argon. The concentration of said tracer, when argon is used, is according to the known art not higher than 5%. That means that a concentration of argon up to 5% allows to use said measurement method, while a concentration higher than 5%, used with the only purpose of measuring the flow rate of the gases is not convenient either from the economic or the metallurgical point of view, and does not offer any improvement in the measurement exactness.